Patent Document 1 describes a device that detects an end point of a surface treatment of a substrate for liquid crystal display. This device irradiates the liquid crystal display with light from a light source such as a xenon lamp or a halogen lamp, detects reflected light from the substrate for liquid crystal display, and detects an end point of a surface treatment from each wavelength's reflectivity of the reflected light.
Patent Document 2 describes a device that obtains the depth of etching in an etched substrate. This device irradiates the etched substrate with light from a white light source such as a xenon lamp and obtains the depth of etching in the etched substrate by detecting reflected light from the etched substrate.